This invention relates to heat exchangers in general and particularly to heat exchangers for ventilating livestock buildings.
Various types of heat exchangers have been developed and utilized in livestock buildings for the purpose of recovering heat from exhausted stale ventilation air and utilizing it to heat incoming fresh ventilation air. Many livestock buildings, particularly those in which farm animals are intensively housed, require constant ventilation to remove moisture, manure odors and gases and gaseous by-products of respiration. Such ventilation is required under the coldest of temperature extremes. It is necessary to heat incoming cold air to maintain acceptable building temperatures for animal growth and comfort. Thus, various heat-exchanging configurations have been developed for the purposes stated above.
Many of these units use a flat plate heat exchange surface with stale air passing on one side and fresh air passing on the other. Various configurations of parallel flow, crossflow, counterflow and reciprocating flow have been used. Typically, the space devoted to such ventilation systems is limited and efforts have been undertaken to minimize the size of these ventilation systems.
Failure to adequately control inlet conditions can result in undesirable drafts on the livestock and condensation on environmental surfaces, leading to poor health and potentially to building deterioration. Good ventilation typically requires the uniform placement and proper adjustment of inlets around the room to be ventilated. They are often mounted on a wall on the outside of a wall or in the ceiling or attic of the building. Control over inlet air velocity usually requires reliance on fans to provide static pressure to induce air movement. Further, it is important to provide uniform distribution of the air throughout the room. However, many existing heat exchangers do not adequately provide for air distribution throughout the room.
In livestock buildings, humidities high enough to cause condensation on the cold heat transfer surfaces are not uncommon. Although the condensation tends to increase heat transfer, it also attracts and traps airborne dust and other materials commonly contained in the air streams. The collected material tends to coat the heat exchange surfaces and, if not properly cleaned, can seriously reduce heat exchange rates. Many existing systems have close spacing between heat exchange surfaces in order to provide sufficient heat exchange area to result in acceptable exchange efficiency. This close spacing increases the likelihood of heat exchanger blinding and makes it more difficult to clean the exchanger surfaces. Furthermore, during times of cold weather, the condensate tends to freeze, thus hindering air flow and heat transfer. Previous attempts to alleviate these problems have not been entirely successful.
It is desirable to use the ductwork of a heat recovery system for velocity cooling during hot weather. The exhaust air fan of the system is turned off when larger summer exhaust fans, which move more air, are in use. Relatively high velocity airstreams can be supplied to animal spaces through the distribution duct or optional extension ducts or drop pipes to individual animal pens. Accordingly, there is no need for heat recovery and thus no need for the counter flow relationship of the incoming and outgoing air. It is desirable to provide a system in which the counter flow section is by-passed and incoming air flows directly to the distribution duct and the like for velocity cooling.
Thus, it is desirable to provide a versatile ventilation heat recovery system which utilizes efficient counterflow heat exchanger geometry. It is also generally desirable to provide a system which is relatively easy to clean and otherwise maintain and is not susceptible to scaling or blinding.